U.S. patent number 7,575,577 [Application Number 10/667,540] was granted by the patent office on 2009-08-18 for devices and methods for the restoration of a spinal disc.
This patent grant is currently assigned to SpineWave. Invention is credited to Lawrence Boyd, Upton L. Maureen.
United States Patent |
7,575,577 |
Boyd , et al. |
August 18, 2009 |
Devices and methods for the restoration of a spinal disc
Abstract
A system and method is provided for maintaining a proper
intervertebral disc height during the replacement or augmentation
of the spinal disc. In one embodiment, a cannulated distractor is
used to distract the adjacent vertebrae and maintain a proper disc
space height. The cannulated distractor is fluidly connected to a
source of fluent material for injection into the disc space. The
distraction includes a distraction tip resident within the disc
space that includes a central lumen and a number of openings
communicating with the lumen to dispense the fluent material within
the disc space.
Inventors: |
Boyd; Lawrence (Durham, NC),
Maureen; Upton L. (Durham, NC) |
Assignee: |
SpineWave (Shelton,
CT)
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Family
ID: |
26989989 |
Appl.
No.: |
10/667,540 |
Filed: |
September 22, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040068268 A1 |
Apr 8, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10282755 |
Oct 29, 2002 |
7004945 |
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60336002 |
Nov 1, 2001 |
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60336333 |
Nov 1, 2001 |
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Current U.S.
Class: |
606/92 |
Current CPC
Class: |
A61F
2/4675 (20130101); A61P 43/00 (20180101); A61P
9/00 (20180101); A61P 3/14 (20180101); A61B
17/8811 (20130101); A61B 17/0218 (20130101); A61B
2017/00469 (20130101); A61B 2017/564 (20130101); A61F
2/442 (20130101); A61B 2017/0256 (20130101); A61F
2002/444 (20130101); A61F 2002/4677 (20130101); A61F
2002/4635 (20130101); A61B 2017/00261 (20130101); A61B
17/3472 (20130101) |
Current International
Class: |
A61B
17/58 (20060101) |
Field of
Search: |
;606/92,93,94,192,61
;604/500,506,164.11 ;424/94.63 ;514/12 ;128/898
;623/17.11,23.67,23.68,17.12 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0277282 |
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Aug 1988 |
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EP |
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2639823 |
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Aug 1990 |
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FR |
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WO 91/00713 |
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Jan 1991 |
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WO |
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WO 99/02214 |
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Jan 1999 |
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WO |
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WO 0049978 |
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Aug 2000 |
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WO |
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WO/01/68005 |
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Sep 2001 |
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WO |
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Other References
EP Search Report for Related European application, EP Serial No.
02773945, Apr. 28, 2008 (5 pages). cited by other .
Premarket Notification {510(k)} Summary, Kyphx Directional
Inflatable Tamp-Traditional 510 (k), Kyphon Inc., Jul. 16, 2003, (5
pgs). cited by other .
510(k) Summary of Safety and Effectiveness, "Kphx Inflatable Bone
Tamp" Jan. 25, 2001, (5 pgs). cited by other .
Boyd, Lawrence M., Mahar, Andrew and Cappello, Joseph, "Injectable
Biomaterials for Augmentation of the Nucleus Pulposus",
International Symposium-Non Fusion Techniques in Spinal Surgery,
Feb. 14, 2003, (12 pgs). cited by other .
Mahar et al., "Biomechanical Efficacy of a Protein Polymer Hydrogel
for Inter-Vertebral Nucleus Augmentation and Replacement", World
Congress on Biomechanics, Calgay, Canada, Aug. 5, 2002, 4 pgs.
cited by other .
Kitchel, Scott and Cappello, Joseph, "Injectable Biomaterials for
Augmentation of the Nucleus Pulposus",
http://127.0.0.1:8080/SAS3C1/presentation.sub.--list.php, Apr. 25,
2005, (6 pgs.). cited by other .
Garfin, Steven R., Yuan, Hansen A. and Reiley, Mark A.,
"Kyphoplasty and Vertebroplasty for the Treatment of Painful
Osteoporotic Compression Fractures", SPINE, vol. 2, No. 14, 2001,
pp. 1511-1515. cited by other .
Lieberman et al., "Initial Outcome and Efficacy of "Kyphoplasty" in
the Treatment of Painful Osteoporotic Vertebral Compression
Fractures", SPINE, vol. 26, No. 14, pp. 1631-1638, 2001, 8 pgs.
cited by other.
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Primary Examiner: Philogene; Pedro
Attorney, Agent or Firm: Maginot, Moore & Beck LLP
Parent Case Text
REFERENCE TO RELATED APPLICATIONS
This application is a continuation of application Ser. No.
10/282,755, filed on Oct. 29, 2002 now U.S. Pat. No. 7,004,945 in
the name of the same inventor, and which claims priority to
provisional application Ser. No. 60/336,002, entitled "Devices,
Methods and Assemblies for Intervertebral Disc Repair and
Regeneration", and provisional application Ser. No. 60/336,333,
entitled "Pretreatment of Cartilaginous Endplates Prior to
Treatment of the Intervertebral Disc with an Injectable
Biomaterial", both of which were filed on Nov. 1, 2001, and the
disclosure of which are both incorporated herein by reference.
Claims
What is claimed is:
1. A kit of parts for sealably introducing fluent material directly
into the disc space having a height between opposed vertebrae
through an opening extending through the annulus fibrosis of said
disc for replacing nucleus pulposus, comprising: a tube having a
passageway for the flow of fluent material therethrough and an
extent adapted to be received in the opening of said annulus
fibrosis, said tube having a seal adapted to engage said annulus
fibrosis adjacent said opening and to form a fluid-tight seal
therewith, wherein said tube extent is defined by a distal tip of
said tube, said distal tip having a dimension greater than the
height of said disc space that is sized and configured to provide
distraction of opposed vertebrae communicating with said disc
space; and a quantity of curable fluent material adapted to be
introduced in a fluid state into said disc space through the
passageway of said tube, said material upon curing having
properties substitutive of the nucleus pulposus.
2. The kit of parts according to claim 1, wherein said seal is
integral with said tube.
3. The kit of parts according to claim 1, wherein said seal is a
separate component mounted on said tube.
4. The kit of parts according to claim 1, wherein said fluent
material is a curable biomaterial selected from the group of
nucleus pulposus substitutes consisting of hyaluronic acid, fibrin
glue, alginates, elastin copolymers and collagen gels.
5. The kit of parts according to claim 1, wherein said distal tip
comprises at least one orifice communicating with said passageway
to provide an exit path for said fluent material into said disc
space.
6. The kit of parts according to claim 1, wherein said distal tip
is removable from said tube.
7. The kit of parts according to claim 6, wherein there are a
plurality of removable distal tips, each being of different
size.
8. The kit of parts according to claim 6, wherein said distal tip
is formed of bioresorbable material.
9. The kit of parts according to claim 1, further including a
syringe adapted to inject said fluent material into the passageway
of said tube.
10. The kit of parts of claim 1, wherein said seal is adapted to
reside within said opening of said annulus fibrosis.
11. The kit of parts according to claim 1, further including an
injector adapted to be coupled to said tube for injecting said
fluent material into said tube under pressure.
12. The kit of parts according to claim 11, wherein said injector
includes a syringe.
13. The kit of parts according to claim 11, wherein said injector
includes a pump.
14. The kit of parts according to claim 11, wherein said injector
includes a mixing chamber.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to the treatment of spinal
diseases and injuries, and more specifically to the restoration of
the spinal disc following surgical treatment. The invention
contemplates devices and methods for restoring the normal
intervertebral disc space height and for facilitating the
introduction of biomaterials for use in the repair and restoration
of the intervertebral disc.
The intervertebral disc is divided into two distinct regions: the
nucleus pulposus and the annulus fibrosus. The nucleus lies at the
center of the disc and is surrounded and contained by the annulus.
The annulus contains collagen fibers that form concentric lamellae
that surround the nucleus and insert into the endplates of the
adjacent vertebral bodies to form a reinforced structure.
Cartilaginous endplates are located at the interface between the
disc and the adjacent vertebral bodies.
The intervertebral disc is the largest avascular structure in the
body. The disc receives nutrients and expels waste by diffusion
through the adjacent vascularized endplates. The hygroscopic nature
of the proteoglycan matrix of the nucleus operates to generate high
intra-nuclear pressure. As the water content in the disc increases,
the intra-nuclear pressure increases and the nucleus swells to
increase the height of the disc. This swelling places the fibers of
the annulus in tension. A normal disc has a height of about 10-15
mm.
There are many causes of disruption or degeneration of the
intervertebral disc that can be generally categorized as
mechanical, genetic and biochemical. Mechanical damage includes
herniation in which a portion of the nucleus pulposus projects
through a fissure or tear in the annulus fibrosus. Genetic and
biochemical causes can result in changes in the extracellular
matrix pattern of the disc and a decrease in biosynthesis of
extracellular matrix components by the cells of the disc.
Degeneration is a progressive process that usually begins with a
decrease in the ability of the extracellular matrix in the central
nucleus pulposus to bind water due to reduced proteoglycan content.
With a loss of water content, the nucleus becomes desiccated
resulting in a decrease in internal disc hydraulic pressure, and
ultimately to a loss of disc height. This loss of disc height can
cause the annulus to buckle with non-tensile loading and the
annular lamellae to delaminate, resulting in annular fissures.
Herniation may then occur as rupture leads to protrusion of the
nucleus.
Proper disc height is necessary to ensure proper functionality of
the intervertebral disc and spinal column. The disc serves several
functions, although its primary function is to facilitate mobility
of the spine. In addition, the disc provides for load bearing, load
transfer and shock absorption between vertebral levels. The weight
of the person generates a compressive load on the discs, but this
load is not uniform during typical bending movements. During
forward flexion, the posterior annular fibers are stretched while
the anterior fibers are compressed. In addition, a translocation of
the nucleus occurs as the center of gravity of the nucleus shifts
away from the center and towards the extended side.
Changes in disc height can have both local and global effects. On
the local (or cellular, level) decreased disc height results in
increased pressure in the nucleus, which can lead to a decrease in
cell matrix synthesis and an increase in cell necrosis and
apoptosis. In addition, increases in intra-discal pressure create
an unfavorable environment for fluid transfer into the disc, which
can cause a further decrease in disc height.
Decreased disc height also results in significant changes in the
global mechanical stability of the spine. With decreasing height of
the disc, the facet joints bear increasing loads and may undergo
hypertrophy and degeneration, and may even act as a source of pain
over time. Decreased stiffness of the spinal column and increased
range of motion resulting from loss of disc height can lead to
further instability of the spine, as well as back pain. The outer
annulus fibrosus is designed to provide stability under tensile
loading, and a well-hydrated nucleus maintains sufficient disc
height to keep the annulus fibers properly tensioned. With
decreases in disc height, the annular fibers are no longer able to
provide the same degree of stability, resulting in abnormal joint
motion. This excessive motion can manifest itself in abnormal
muscle, ligament and tendon loading, which can ultimately be a
source of back pain.
Radicular pain may result from a decrease in foraminal volume
caused by decreased disc height. Specifically, as disc height
decreases, the volume of the foraminal canal, through which the
spinal nerve roots pass, decreases. This decrease may lead to
spinal nerve impingement, with associated radiating pain and
dysfunction
Finally, adjacent segment loading increases as the disc height
decreases at a given level. The discs that must bear additional
loading are now susceptible to accelerated degeneration and
compromise, which may eventually propagate along the destabilized
spinal column.
In spite of all of these detriments that accompany decreases in
disc height, where the change in disc height is gradual many of the
ill effects may be "tolerable" to the spine and may allow time for
the spinal system to adapt to the gradual changes. However, the
sudden decrease in disc volume caused by the surgical removal of
the disc or disc nucleus may heighten the local and global problems
noted above. Many disc defects are treated through a surgical
procedure, such as a discectomy in which the nucleus pulposus
material is removed. During a total discectomy, a substantial
amount (and usually all) of the volume of the nucleus pulposus is
removed and immediate loss of disc height and volume can result.
Even with a partial discectomy, loss of disc height can ensue.
Discectomy alone is the most common spinal surgical treatment,
frequently used to treat radicular pain resulting from nerve
impingement by disc bulge or disc fragments contacting the spinal
neural structures.
In another common spinal procedure, the discectomy may be followed
by an implant procedure in which a prosthesis is introduced into
the cavity left in the disc space when the nucleus material is
removed. Thus far, the most prominent prosthesis is a mechanical
device or a "cage" that is sized to restore the proper disc height
and is configured for fixation between adjacent vertebrae. These
mechanical solutions take on a variety of forms, including solid
kidney-shaped implants, hollow blocks filled with bone growth
material, push-in implants and threaded cylindrical cages.
In more recent years, injectable biomaterials have been more widely
considered as an augment to a discectomy. As early as 1962, Alf
Nachemson suggested the injection of room temperature vulcanizing
silicone into a degenerated disc using an ordinary syringe. In
1974, Lemaire and others reported on the clinical experience of
Schulman with an in situ polymerizable disc prosthesis. Since then,
many injectable biomaterials or scaffolds have been developed as a
substitute for the disc nucleus pulposus, such as hyaluronic acid,
fibrin glue, alginate, elastin-like polypeptides, collagen type I
gel and others. A number of patents have issued concerning various
injectable biomaterials including: cross-linkable silk elastin
copolymer discussed in U.S. Pat. No. 6,423,333 (Stedronsky et al.);
U.S. Pat. No. 6,380,154 (Capello et al.); U.S. Pat. No. 6,355,776
(Ferrari et al.); U.S. Pat. No. 6,258,872 (Stedronsky et al.); U.S.
Pat. No. 6,184,348 (Ferrari et al.); U.S. Pat. No. 6,140,072
(Ferrari et al.); U.S. Pat. No. 6,033,654 (Stedronsky et al.); U.S.
Pat. No. 6,018,030 (Ferrari et al.); U.S. Pat. No. 6,015,474
(Stedronsky); U.S. Pat. No. 5,830,713 (Ferrari et al.); U.S. Pat.
No. 5,817,303 (Stedronsky et al.); U.S. Pat. No. 5,808,012
(Donofrio et al.); U.S. Pat. No. 5,773,577 (Capello); U.S. Pat. No.
5,773,249 (Capello et al.); U.S. Pat. No. 5,770,697 (Ferrari et
al.); U.S. Pat. No. 5,760,004 (Stedronsky); U.S. Pat. No. 5,723,588
(Donofrio); U.S. Pat. No. 5,641,648 (Ferrari); and U.S. Pat. No.
5,235,041 (Capello et al.); protein hydrogel described in U.S. Pat.
No. 5,318,524 (Morse et al.); U.S. Pat. No. 5,259,971 (Morse et
al.); U.S. Pat. No. 5,219,328 (Morse et al.); and U.S. Pat. No.
5,030,215; polyurethane-filled balloons discussed in No. 60/004,710
(Felt et al.); U.S. Pat. No. 6,306,177 (Felt et al.); U.S. Pat. No.
6,248,131 (Felt et al.) and U.S. Pat. No. 6,224,630 (Bao et al.);
collagen-PEG set forth in U.S. Pat. No. 6,428,978 (Olsen et al.);
U.S. Pat. No. 6,413,742 (Olsen et al.); U.S. Pat. No. 6,323,278
(Rhee et al.); U.S. Pat. No. 6,312,725 (Wallace et al.); U.S. Pat.
No. 6,277,394 (Sierra); U.S. Pat. No. 6,166,130 (Rhee et al.); U.S.
Pat. No. 6,165,489 (Berg et al.); U.S. Pat. No. 6,123,687 (Simonyi
et al.); U.S. Pat. No. 6,111,165 (Berg); U.S. Pat. No. 6,110,484
(Sierra); U.S. Pat. No. 6,096,309 (Prior et al.); U.S. Pat. No.
6,051,648 (Rhee et al.); U.S. Pat. No. 5,997,811 (Esposito et al.);
U.S. Pat. No. 5,962,648 (Berg); U.S. Pat. No. 5,936,035 (Rhee et
al.); and U.S. Pat. No. 5,874,500 (Rhee et al.); chitosan in U.S.
Pat. No. 6,344,488 to Chenite et al.; a variety of polymers
discussed in U.S. Pat. No. 6,187,048 (Milner et al.; recombinant
biomaterials in No. 60/038,150 (Urry); U.S. Pat. No. 6,004,782
(Daniell et al.); U.S. Pat. No. 5,064,430 (Urry); U.S. Pat. No.
4,898,962 (Urry); U.S. Pat. No. 4,870,055 (Urry); U.S. Pat. No.
4,783,523 (Urry et al.); U.S. Pat. No. 4,783,523 (Urry et al.);
U.S. Pat. No. 4,589,882 (Urry); U.S. Pat. No. 4,500,700 (Urry);
U.S. Pat. No. 4,474,851 (Urry); U.S. Pat. No. 4,187,852 (Urry et
al.); and U.S. Pat. No. 4,132,746 (Urry et al.); and annulus repair
materials described in U.S. Pat. No. 6,428,576 to Haldimann.
These references disclose biomaterials or injectable scaffolds that
have one or more properties that are important to disc replacement,
including strong mechanical strength, promotion of tissue
formation, biodegradability, biocompatibility, sterilizability,
minimal curing or setting time, optimum curing temperature, and low
viscosity for easy introduction into the disc space. The scaffold
must exhibit the necessary mechanical properties as well as provide
physical support. It is also important that the scaffold be able to
withstand the large number of loading cycles experienced by the
spine. The biocompatibility of the material is of utmost
importance. Neither the initial material nor any of its degradation
products should elicit an unresolved immune or toxicological
response, demonstrate immunogenicity, or express cytoxicity.
Generally, the above-mentioned biomaterials are injected as viscous
fluids and then cured in situ. Curing methods include
thermosensitive cross-linking, photopolymerization, or the addition
of a solidifying or cross-linking agent. The setting time of the
material is important--it should be long enough to allow for
accurate placement of the biomaterial during the procedure yet
should be short enough so as not to prolong the length of the
surgical procedure. If the material experiences a temperature
change while hardening, the increase in temperature should be small
and the heat generated should not damage the surrounding tissue.
The viscosity or fluidity of the material should balance the need
for the substance to remain at the site of its introduction into
the disc, with the ability of the surgeon to manipulate its
placement, and with the need to assure complete filling of the
intradiscal space or voids.
Regardless of the injectable scaffold material used, it is critical
that the completed procedure restore the disc height. It is thus
important that the proper disc height be maintained while the
biomaterial is being introduced into the intradiscal space.
Ideally, the disc height will be restored to levels equivalent to
the heights of the adjacent discs and representative of a normal
spinal disc height for the particular patient.
However, if disc height is not re-established prior to introduction
of the scaffold material, it will become impossible to replace the
lost disc volume and at least restore the disc height to what it
was prior to the discectomy. Failure to hold a proper disc height
as the biomaterial is introduced and cured in situ can eventually
lead to a collapse of the disc space. This phenomenon is
illustrated by a comparison of a proper intervertebral disc height
in FIG. 1a versus a reduced disc height in FIG. 1b. The reduced
disc height of FIG. 1b will ordinarily follow a substantially
complete discectomy, unless the adjacent vertebrae are distracted.
The patient can be placed in certain positions that tend to open
the disc space, particularly at the posterior side of the disc D.
However, it has been found that even with hyper-flexion of the
spine the intervertebral space does not approach its proper volume,
and consequently the intervertebral height does not approach the
proper disc height of FIG. 1a.
Prior procedures for the implantation of a curable disc prosthesis
have relied upon the physical positioning of the patient or upon
pressurized injection of the biomaterial to obtain some degree of
distraction. However, these prior approaches do not achieve
repeatable restoration of proper anatomical disc height, either
during the surgical procedure or afterwards. Consequently, there
remains a need for a method and system that provides a high degree
of assurance that a proper disc height will be established and
maintained when the intervertebral disc is replaced or augmented by
an injectable biomaterial.
SUMMARY OF THE INVENTION
In order to address the unresolved needs of prior spinal
procedures, the present invention contemplates a method for
injecting a fluent material into a disc space. The method includes
the steps of creating a portal in the annulus pulposus in
communication with the intradiscal space and impacting a cannulated
distractor into the portal. In accordance with one feature of the
invention, the distractor is configured to distract the vertebrae
adjacent the intradiscal space and to establish a disc space height
between the adjacent vertebrae. The method includes the further
step of introducing the fluent material into the intradiscal space
through a lumen of the cannulated distractor while the distractor
maintains the established disc space height.
In certain embodiments, the inventive method includes the step of
performing a discectomy after the portal is created, in which the
discectomy forms a cavity within the intradiscal space. In this
embodiment, the step of impacting a cannulated distractor includes
positioning the distractor so that the lumen is in communication
with the cavity, and the step of introducing the fluid includes
introducing the fluid into the cavity. The discectomy can be a
total discectomy in which substantially all of the nucleus pulposus
is removed from the disc space.
In a further feature of the invention, the fluent material is a
curable biomaterial that is particularly suited as a disc
replacement or augmentation material. In this case, the step of
introducing the fluent material can include maintaining the
distractor in its impacted position until the biomaterial cures in
situ. In other words, the cannulated distractor maintains the
adjacent vertebrae in their distracted position until the
biomaterial has set. In this way, the proper disc height can be
maintained and retained once the biomaterial has set and the
distractor removed.
In certain embodiments, the fluent material can be introduced into
the disc cavity under pressure. In another feature of the invention
that is particularly useful where the fluent material is under
pressure, the cannulated distractor is configured to seal the
portal when the distractor is impacted therein. In some
embodiments, the distractor has a portion sized to substantially
block or seal the annular portal. In other embodiments, the
distractor includes a sealing feature that bears against the
adjacent vertebrae and/or the annulus fibrosus material surrounding
the portal. The sealing feature can be integral with the cannulated
distractor or can include a separate component, such as a seal
ring, mounted on the distractor.
In still another aspect of the invention, and again one that is
particularly suited where the fluent material is under pressure, a
vent is provided in the cannulated distractor. Thus, the fluent
material can be introduced into the intradiscal space until the
fluent material seeps from the vent. Thus, the vent can provide an
immediate indication that the disc cavity is full.
In some embodiments of the invention, the cannulated distractor is
engaged to a fluid injector apparatus. This apparatus can be in a
variety of forms, including a pump, a syringe and a gravity feed
system.
In other embodiments, the step of introducing the fluent material
includes extending an tube through the lumen in the cannulated
distractor, with the tube fluidly connected to a source of the
fluent material. The tube can be manipulated through the distractor
lumen to direct the fluent material to specific locations within
the disc cavity. For instance, the tube can be moved through a
seeping motion so that the fluent material is completely dispersed
throughout the disc space. At the same time, the tube can be
gradually withdrawn from the distractor lumen as the fluent
material nears the lumen opening.
In a preferred embodiment, a seal is provided between the tube and
the lumen. A vent can then be provided separate from the lumen so
that the fluent material can seep from the vent to indicate that
the cavity is full.
In another embodiment of the invention, a device for injecting a
fluent material into a disc space comprises a distraction member
having opposite surfaces configured to distract adjacent vertebrae
to the disc space. The distraction member has a proximal end and a
distal end portion, in which at least the distal end portion
configured to be disposed within the disc space. The distraction
member further defines a fluid passageway between the proximal end
and the distal end portion, the passageway having an opening at the
proximal end and at the distal end portion. In some embodiments,
the distraction member can include a fitting associated with the
proximal end of the distraction member for fluidly connecting the
distraction member to a source of the fluent material.
In accordance with another aspect of the invention, the device
further comprises an elongated cannula defining a lumen
therethrough. The cannula can have a first fitting at one end
thereof configured for fluid tight connection to the fitting of the
distraction member, and a second fitting at an opposite end thereof
configured for fluid connection to a source of the fluent material.
In specific embodiments, the distraction member is integral with
the cannula and the second fitting is the fitting associated with
the proximal end of the distraction member. In other embodiments,
the distraction member is removable from the cannula.
In a preferred embodiment, at least the distal end portion of the
distraction member is bullet-shaped. In alternative embodiments,
the distal end portion of is wedge-shaped with opposite
substantially flat sides, cruciate-shaped, I-beam shaped and
C-shaped.
The fluid passageway of the distraction member includes a central
lumen with a number of openings communicating therewith. The
openings can be arranged in the variously shaped distal end portion
to direct the fluent material to appropriate locations within the
disc cavity. The distraction member can also define a vent opening
separate from the fluid passageway. In certain embodiments, the
fluid passageway can be in the form of interconnected interstices
throughout the distraction member material.
In the preferred embodiment, the distraction member is formed of a
biocompatible material, such as stainless steel or titanium. In
alternative embodiments, other biocompatible materials can be used,
such as polymeric materials and even bioresorbable materials. In
accordance with one aspect, the distraction member is configured to
be removed from the disc space once the fluent material has been
introduced into the disc cavity, and has cured, if necessary. In
other aspects, the distraction member is configured to remain
within the disc space, most preferably if the member is formed of a
bioresorbable material.
The distraction member can include a sealing element associated
with a proximal portion of the distal end portion, wherein the
sealing element is configured to provide a substantially
fluid-tight seal within the disc space. The sealing element can
include a number of seal rings disposed on the distal end portion.
The seal rings can be integral with the distal end portion or can
be elastomeric rings mounted on the distal end portion, for
example.
It is one object of the invention to provide a system and device
for maintaining and enforcing a proper intervertebral spacing or
disc height when a disc prosthesis is introduced into a cavity
within the intradiscal space. Another object is achieved by
features of the invention that allow introduction of a fluent
material into the disc space while maintaining the adjacent
vertebrae distracted and the disc height intact.
Other objects and certain benefits of the invention can be
discerned from the following written description and accompanying
figures.
DESCRIPTION OF THE FIGURES
FIGS. 1a-1b are lateral views of a disc and adjacent vertebrae
showing a proper intervertebral disc height (FIG. 1a) and a reduced
disc height (FIG. 1b) following a substantially complete
discectomy.
FIG. 2 is a lateral view a disc and adjacent vertebrae with a guide
wire placed in accordance with one aspect of the present
invention.
FIG. 3 is a sagittal view of the disc space shown in FIG. 2 with a
trephine forming a portal in the annulus fibrosus of the disc.
FIG. 4 is a sagittal view of the disc space shown in FIG. 3 with a
tissue extraction device positioned within the nucleus pulposus of
the disc.
FIG. 5 is a sagittal view of the disc space shown in FIGS. 2-4 with
a cannulated distractor in accordance with one embodiment of the
present invention.
FIG. 6 is a side view of a cannulated distractor in accordance with
one embodiment of the present invention.
FIG. 7 is a lateral view of the disc space shown in FIGS. 2-5 with
the cannulated distractor of FIG. 6 positioned within the disc
space.
FIG. 8 is a perspective view of a distraction tip forming part of
the cannulated distractor shown in FIGS. 6 and 7.
FIG. 9 is a perspective view of a distraction tip according an
alternative embodiment of the invention.
FIG. 10 is a side view of an injector apparatus for use in one
embodiment of the invention.
FIG. 11 is lateral view of a disc space with a cannulated
distractor in accordance with a further embodiment of the
invention.
FIG. 12 is a cross-sectional view of a cruciate distraction tip
according to one embodiment of the cannulated distractor of the
present invention.
FIG. 13 is a cross-sectional view of an I-beam shaped distraction
tip according to another embodiment of the cannulated distractor of
the present invention.
FIG. 14 is a cross-sectional view of a C-shaped distraction tip
according to a further embodiment of the cannulated distractor of
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
For the purposes of promoting an understanding of the principles of
the invention, reference will now be made to the embodiments
illustrated in the drawings and described in the following written
specification. It is understood that no limitation to the scope of
the invention is thereby intended. It is further understood that
the present invention includes any alterations and modifications to
the illustrated embodiments and includes further applications of
the principles of the invention as would normally occur to one
skilled in the art to which this invention pertains.
The present invention contemplates a procedure and device that is
implemented following removal of a portion or substantially all of
the natural nucleus pulposus of an intervertebral disc. One
important purpose of the invention is to maintain the proper disc
height during the introduction of a biomaterial that is intended to
replace the removed nuclear material. Removal of disc material can
be accomplished chemically, such as by the use of Chymopapain.
However, the more common approach is by discectomy, which can be
conducted as an open surgical procedure, via microscope-assisted
visualization, or through percutaneous access.
A typical percutaneous discectomy procedure is illustrated in FIGS.
2-4. In the first step, a guide wire G is directed into an affected
disc D between two vertebrae, such as the L2 and L3 lumbar
vertebrae. As shown in FIG. 3, the guide wire G penetrates the
annulus fibrosus A and the nucleus pulposus N, and it preferably
anchored at opposite sides of the annulus A. The guide wire G can
be positioned and placed under indirect vision, such as
fluoroscopy, or stereotactically, or using other known procedures
for properly orienting the guide wire within the spinal disc D. The
procedure shown in the figures utilizes a posterior approach, which
is preferable for implementation of the present invention. Of
course, other approaches may be utilized for the discectomy in
accordance with known surgical procedures. In addition, the access
location may be dictated by the location of a fissure or herniation
of the disc.
A trephine T is advanced over the guide wire and driven through the
annulus A, thereby forming a portal into the disc nucleus. As shown
in FIG. 4, a tissue removal device R can be advanced through the
trephine T or through a working channel cannula aligned with the
disc portal. The device R can then be used to remove all or part of
the nucleus N of the disc D. As depicted in dashed lines in FIG. 4,
a second trephine T' can be used to create a second annular portal
to facilitate complete removal of the nucleus pulposus of the disc.
The tissue removal device R can be of a variety of types, such as a
rongeur, tissue morcellator, rotary and/or reciprocating
vacuum-assisted cutter, and even a chemical introducer to direct a
chemical such as Chymopapain into the nuclear space. Removal of the
nucleus leaves a cavity C (see FIG. 5) surrounded by the
substantially intact annulus A
The present invention contemplates the introduction of a
biomaterial into the disc cavity C that is capable or restoring
disc height and preferably substantially normal disc function. For
instance, any of the biomaterials discussed above can fill the
newly formed cavity. In accordance with the preferred embodiment,
the biomaterial is a fluid with an appropriate flowability and/or
viscosity. In particular, the biomaterial must have sufficient
flowability to permit relatively easy introduction into the disc
cavity C, but with sufficient viscosity to hold its shape within
the disc. Since the material being used to fill the disc cavity C
is a fluid, the present invention provides means for holding a
proper disc height as the material flows into the cavity, to
thereby ensure that the cavity is filled--i.e., that the volume of
implant biomaterial is the same as the volume of nucleus pulposus
removed in the discectomy. Moreover, the methods and devices of the
invention provide a means for maintaining the cavity volume as the
biomaterial transforms to its solid state.
Thus, in accordance with one embodiment of the invention, a
cannulated distractor 10 is provided as shown in FIGS. 5-8. The
distractor 10 includes a distal end 12 that extends into the disc
cavity C and a proximal end 14 that is configured to engage a
device for injecting the biomaterial into the disc space. The
distractor 10 includes a cannula 11 that terminates in a
distraction tip 18 at the distal end of the device. A lumen 16 is
defined along the entire length of the device from the proximal end
14 to the and through the distraction tip 18. The distraction tip
18 is sized to extend through the portal formed in the disc annulus
A (see FIG. 3). The distractor 10 can include a shoulder 20
proximal to the distraction tip 18, in which the shoulder is sized
to prevent passage through the annular portal. The shoulder 20 can
operate to limit the distance that the distraction tip 18 extends
into the disc cavity C. The distractor 10 can be provided with
means for temporarily fixing the distractor in position or
supporting the distractor on the adjacent vertebrae.
As shown in FIG. 7, the distraction tip 18 is intended to be
inserted through the annular portal and is configured to restore
the appropriate intradiscal height in the cavity C. Thus, in one
embodiment, the distraction tip 18 can include a tapered leading
portion 24. This leading portion 24 can be introduced into the
cavity C and as the tip is advanced further into the cavity the
leading portion will gradually distract the adjacent vertebrae as
the leading portion 24 bears against the disc endplates E. In a
specific embodiment, the tapered portion 24 can be substantially
bullet-shaped, as shown in FIG. 8. With this configuration, the
distraction tip 18 can have any rotational orientation when the tip
is inserted through the annular portal.
Alternatively, the distraction tip can be configured like the tip
40 shown in FIG. 9. With this embodiment, the tip includes opposing
generally flat sides 50 and intermediate edges 52 of the wedge
portion 42. The tip 40 can be introduced into the disc space with
the flat sides 50 of the wedge facing the disc endplates E. Once
the tip is fully within the disc cavity C, the tip can be rotated
so that the edges 52 contact and distract the endplates. The edges
52 themselves can be wedge-shaped, having a greater width at their
proximal end than at their distal end.
Returning to FIGS. 6-8, in accordance with one feature of the
invention, the distraction tip 18 includes a number of side
orifices 30 and an end orifice 32 that all communicate with the
central lumen 16. As depicted in FIG. 7, the orifices 30, 32
provide an exit path for fluid injected through the lumen 16.
Preferably, the orifices are oriented to be unobstructed by the
vertebral endplates E. The distraction tip 40 shown in FIG. 9 is
also provided with side orifices 46 in the flat sides 50 and an end
orifice 48. With this embodiment, the edges 52 need not include
orifice(s) because the edges will be occluded by contact the
endplates.
Since fluid is intended for introduction through the distraction
tip 30, it is preferable that some feature be provided to ensure a
substantially fluid-tight seal at the entrance to the disc cavity C
through the annular portal. Thus, in one embodiment of the
invention, the distraction tip 30 can include annular rings 26 that
are intended to bear against the disc endplates E and/or the disc
annulus A in a sealing relationship. The rings 26 can be integral
with the distraction tip 30, or can be separate components mounted
on the distraction tip, such as in the form of elastomeric seal
rings. The seal rings can be mounted within annular grooves formed
in the distraction tip.
The distractor 10 includes a fitting 36 defined at the proximal end
14 of the cannula 11. The fitting 36 provides means for making a
fluid-tight connection with a device adapted to inject the
biomaterial into the disc. One exemplary device 70 is shown in FIG.
10. The injector 70 includes a chamber 72 for storage of the
biomaterial. In some cases, the chamber 72 may constitute multiple
chambers where the injectable biomaterial is obtained by mixing
various constituent materials. For instance, certain materials may
be curable in situ and may require combining a curing agent with a
base material. To facilitate mixing of the biomaterial
constituents, the injector 70 can include a mixing chamber 74. A
manual control 76 can be provided that forces the contents of the
chamber 72 into the mixing chamber 74. Alternatively, the injector
70 can incorporate a mechanism that drives the fluid from the
injector under pressure, such as a syringe or a pump.
The injector 70 includes a fitting 80 that is configured for
fluid-tight engagement with the fitting 36 of the cannulated
distractor 10. In a preferred embodiment, the two fittings 36, 80
represent mating components of a LUER.RTM. fitting. The injector
can include a nozzle 78 that extends into the cannula 11, or more
specifically into the lumen 16, when the injector 70 is engaged to
the cannulated distractor. A grip 82 can be provided to allow
manual stabilization of the injector.
As explained above, the cannulated distractor 10 of the present
invention may be utilized after a discectomy procedure. For
purposes of illustration, it has been assumed that a total
discectomy has been performed in which substantially all of the
nucleus pulposus has been removed, leaving a disc cavity C as shown
in FIG. 5. Of course, the principles of the invention can apply
equally well where only a portion of the disc nucleus has been
removed through a partial discectomy. If a bilateral approach has
been used (as represented by the first and second trephines T and
T'), one of the annular portals can be sealed with a material
compatible to the disc annulus fibrosus. When the nucleus has been
cleared, the guide wire G can be repositioned within the disc D,
again preferably using known guidance and positioning instruments
and techniques. The cannulated distractor 10 can then be advanced
over the guide wire until the distraction tip 18 is properly
situated within the nuclear cavity C. Preferably, the proper depth
for the distraction tip 18 can be determined by contact of the
shoulder 20 with the outer annulus A, or by contact of an
associated depth feature with the adjacent vertebral bodies.
With the distraction tip 18, the tapered portion 24 gradually
separates the adjacent vertebral endplates E as the distraction tip
is driven further into the disc space. A mallet, impactor or other
suitable driver can be used to push the tapered portion 24 into
position against the natural tension of the disc annulus. It is
understood that the goal of this step is to fully distract the
intervertebral space to a proper disc height for the particular
spinal level. For instance, for the L2-L3 disc space, the
appropriate disc height may be 13-15 mm, so that the distraction
tip is positioned within the cavity C to achieve this amount of
distraction. As shown in FIG. 5, preferably only one cannulated
distractor 10 is utilized, since the distraction tip 18 necessarily
occupies a certain portion of the volume of the cavity C. However,
a second cannulated distractor and associated distraction tip may
be necessary (such as through a second annular portal as shown in
FIG. 4) to achieve the proper disc height.
It should be understood that the process thus far would be similar
for the distraction tip 40. However, unlike the tapered distraction
tip 18, the distraction tip 40 requires an additional step to
distract the disc space. Specifically, the distraction tip 40 is
initially inserted with its flat sides 50 facing the endplates E.
The tip must then be rotated until the edges 52 bear against and
support the endplates. The flat sides 50 can include an angled
transition to the edges, or the edges 52 can be rounded to
facilitate the distraction as the distraction tip is rotated in
situ.
When the distraction tip, such as tip 10, is inserted to its proper
depth within the disc cavity C, the annular portal is sealed,
whether by contact with the shoulder 20, or by engagement of the
rings 26 with the endplates E or the interior of the annular
portal. At this point, the biomaterial fluid can be injected into
the cannulated distractor, and specifically into the lumen 16. To
accomplish this step, the injector, such as injector 70, can be
mated with the fitting 36 at the proximal end 14 of the cannulated
distractor. Optimally, the guide wire G is removed and the fitting
80 of the injector engages the fitting 36. The nozzle 78 extends
into the lumen 16. The nozzle can be sized so that the exit end of
the nozzle is near or within the distraction tip 18. At this point,
the injector 70 can be actuated in accordance with its construction
so that the biomaterial fluid is displaced from the injector and
into the lumen 16. The biomaterial exits through the orifices 30,
32 in the distraction tip 18 to fill the cavity C. The orifices 30,
32 are preferably positioned and sized to achieve complete and
rapid dispersion of the biomaterial throughout the cavity. Again,
the goal of this step of the process is to completely fill the
entire volume of the cavity, or to replace the entire volume of
nucleus pulposus removed during the discectomy. Where the fluid
biomaterial is an in situ curable or settable material, time may
also be of the essence to ensure a homogeneous mass once the
material is completely cured.
It should be apparent that the distraction tip 18, 40 maintains the
proper disc height while the biomaterial is injected. The tip can
be retained in position until the injected material cures or sets.
Once the material has sufficiently cured, the distraction tip 18,
40 can be removed. Since the distraction tip occupies a certain
volume, additional biomaterial can be injected through the tip as
it is being withdrawn, if required, thereby filling the gap left by
the tip.
In certain embodiments, the distraction tip 18 can be a modular and
removable from the cannula 11, as shown in FIG. 8. Thus, the tip 18
and cannula 11 can be provided with a removable mating element 19,
such as a press-fit (as shown in FIG. 9) or a threaded or LUER.RTM.
type fitting (not shown) as would occur to a person of skill in
this art. A removable distraction tip can serve several purposes.
In one purpose, the injected biomaterial may require a lengthy
curing time. While the material is curing, it is of course
necessary to keep the distraction tip in position to maintain the
proper disc height. However, it may not be necessary to retain the
other components of the system in position, such as the injector 70
and cannula 11. A modular distraction tip allows the cannula 11 to
be removed while the tip remains in position, acting as a disc
spacer while the biomaterial cures.
In another purpose, a number of differently sized tips can be
mounted to a commonly sized cannula. Each patient has a different
spinal anatomy, which means the appropriate disc height at a given
spinal level may vary between patients. Moreover, the disc height
can vary with spinal level. Thus, a plurality of differently sized
distraction tips 18 can be provided to ensure proper spacing across
the spinal disc D.
Another purpose behind a removable distraction tip 18 is achieved
by embodiments in which the tip is formed of a biocompatible
material that allows the tip to remain resident within the disc
space. In this embodiment, the distraction tip material must be
compatible with the biomaterial used to replace the natural
nucleus. For instance, if the biomaterial is only intended to
restore disc height, but not the natural biomechanical properties
of the natural nucleus, then the material of the distraction tip 18
may provide a generally rigid scaffolding. On the other hand, and
most preferably, the injected biomaterial is intended to emulate
the biomechanical characteristics of the disc to allow the spinal
segment to operate as close to a normal spinal segment as possible.
In this instance, a rigid scaffold would of course frustrate the
normal flexion, compression and torsional responses of the disc.
Thus, the distraction tip 18 in embodiments where the tip is left
in situ can be formed of a biodegradable or bioresorbable material
that absorbs into the matrix of the cured biomaterial forming the
disc nucleus prosthesis.
Whether the distraction tip is removed or remains within the disc
space, it is preferable that the tip occupy as little volume as
possible. On the other hand, the distraction tip must be
sufficiently strong to sustain the compression loads that it will
face while distracting adjacent vertebrae and holding the disc
space height while the injected biomaterial cures. In the specific
embodiments shown in FIGS. 5 and 7, the distraction tip 18 is shown
traversing across a substantial portion of the nuclear cavity C.
Alternatively, the distraction tip can have a reduced length from
the shoulder 20 so that the tip extends only partially into the
cavity. Distraction of the disc space can be abetted by certain
positions of the patient on the operating table where, for
instance, the anterior aspect of the disc space is naturally
distracted by the position of the spine. Proper distraction of the
disc space may be better accommodated by an anterior approach,
rather than the posterior approach shown in FIGS. 5 and 7.
In alternative embodiments, the distraction tip can assume a wide
range of geometries, some dictated by the annular portal formed
during the discectomy procedure. In the embodiment of FIGS. 5-8, a
circular annular portal has bee created and a circular distraction
tip 18 utilized to seal the portal. In some cases, a planar or
wedge-shaped distraction tip, similar to the tip 40 shown in FIG.
9, can be utilized where the opening through the annulus has an
area greater than the tip itself. In these cases, the extra space
between the tip and the interior surface of the portal can provide
an opening for a direct visualization instrument, or some other
appropriate instrument. Preferably, this approach is better suited
where the biomaterial is not injected under pressure, such as cases
where a gravity feed is employed (see FIG. 11 and associated
discussion below).
In other cases, surgeons perform the discectomy through rectangular
or cruciate portals in the disc annulus. A complementary shaped
distraction tip can be utilized to conform to and fill the annular
portal. For instance, the distraction tip can assume the
configuration shown in FIGS. 12-14. A cruciate-shaped tip 55 is
shown in FIG. 12 with a central lumen 56 communicating with a
number of openings 56. It is understood that the arms of the
cruciate-shaped tip can have a thinner cross-section than shown in
the figure, provided they are sufficiently strong to support the
adjacent vertebrae in their proper distracted position. Likewise,
the openings 56 can be distributed in a variety of patterns through
the hub and legs of the cruciate shape.
An I-beam distraction tip 60 is shown in FIG. 13 having a central
lumen 61 communicating with a number of openings 62. The
distraction tip 63 in FIG. 14 has a C shape and includes a lumen 64
and openings 65. These two beam configurations provide sufficient
support for the necessary distraction. Again, the thickness of the
arms of the beams can be reduced as necessary to minimize the
cross-section of the distraction tip 60, 63.
Regardless of the overall configuration of the distraction tip, it
is most preferable that volume of the tip within the nuclear cavity
C be minimized. The bullet-shaped tip, such as tip 18, may be less
desirable from that standpoint, while the wedge type, such as tip
40, may be preferable. In addition, regardless of the overall
configuration, the distraction tip must communicate with the lumen
16 and must provide some means for discharge of the biomaterial
fluid through the tip. In the illustrated embodiments, the
distraction tips 18, 40 include orifices 30, 31 and 46, 48,
respectively, that communicate with the corresponding lumens 16,
44. Alternatively, the distraction tips can be in the form of an
open scaffold or skeletal framework. Again, the scaffold or
framework must be sufficiently strong, especially in compression,
to properly distract the disc space and hold the disc height for an
appropriate length of time. In some embodiments, the distraction
tip can be formed of a material having interconnected interstices,
such as a porous material. The porous distraction tip can present a
solid scaffold with a multitude of fluid flow paths through the
material. The porous material can be a metal, such as a porous
tantalum; however, a porous polymer, such as polylactic acid, is
preferred so that the scaffold does not obscure visualization of
the disc space after the procedure is completed.
In the procedures discussed above, the distraction tip has been
described as providing an avenue for the injection of a biomaterial
into the nuclear cavity C following a discectomy procedure. The
distraction tips of the present invention serve equally well as a
conduit for the introduction of other fluids to the disc space. For
instance, the distraction tips can be used to inject a biomaterial
such as the material disclosed in provisional application Serial
No. 60/336,332, entitled "Pretreatment of Cartilaginous Endplates
Prior to Treatment of the Intervertebral Disc with an Injectable
Biomaterial", mentioned above, the disclosure of which is
incorporated herein by reference. This provisional application
discloses materials for the pretreatment of the disc endplates, for
instance, to improve the biological functioning of a degenerative
disc. The cannulated distractors of the present invention, such as
distractor 10, can be initially used for the disc pretreatments
disclosed in the above-mentioned provisional application. Once the
pretreatment has been completed, the cannulated distractor can then
be used for the injection of the curable biomaterial.
Likewise, the present inventive cannulated distractor can be used
for multiple fluid injections, including multiple injections to
effect curing of a biomaterial within the nuclear cavity C. For
instance, certain biomaterials may include a first constituent that
is introduced into the disc space, followed by a second constituent
or curing agent. The second constituent can initiate curing of the
resulting composition.
An alternative embodiment of the invention is depicted in FIG. 11.
In this embodiment, a cannulated distractor 85 is provided that
includes a generally frusto-conical distraction tip 86 and a
shoulder 87. The tip 86 is configured to act as a wedge to distract
the disc space as the cannulated distractor 86 is impacted into the
disc space. The shoulder 87 acts as a stop against the adjacent
vertebral bodies to limit the distance that the tip is driven into
the disc space. Preferably, the distraction tip 86 has a length
from the shoulder 87 to its distal end that is sufficient to span
the length of the portal in the disc annulus A, but is limited in
its extent into the nuclear cavity C. With this embodiment, the
distraction tip 86 does not displace any significant volume within
the cavity C.
The cannulated distractor 85 defines a lumen 88 extending the
entire length of the distractor. The lumen 88 is sized to receive
an injection tube 94 therethrough. The injection tube 94 can
include a fitting 96 for engaging an injection apparatus 98. The
fitting 96 can be of any suitable type, such as the LUER.RTM.
fitting mentioned above. The injection apparatus can be similar to
the injector 70 shown in FIG. 10, or can assume a variety of
configurations for the introduction of a fluid into the disc
cavity. In one embodiment of the invention, the biomaterial fluid
is introduced into the cavity by way of gravity feed. In this
instance, the injection apparatus 98 can be simply in the form of a
reservoir with an atmospheric vent to allow the biomaterial to flow
downward into the disc space by gravity alone. Of course, the
patient must be properly presented to accommodate gravity filling
of the disc cavity C.
In this embodiment, the cannulated distractor 85 operates as a
support or guide for the injection tube 94. The tube 94 can be in
the form of a smooth tipped, relatively large gauge needle that is
sized to accommodate optimum flow of the biomaterial into the disc
space. The tube 94 can be introduced through and gradually
withdrawn from the cannulated distractor 85 (as indicated by the
arrow in FIG. 11) as the biomaterial flows into the cavity C. In
addition, the diameter of the tube 94 can be sized relative to the
diameter of the lumen 88 so that the discharge opening 95 of the
tube 94 can be pivoted with a sweeping motion through the cavity C.
This aspect of this embodiment facilitates complete direct filling
of the disc cavity C with the biomaterial. Where the cannulated
distractor is used to introduce pre-treatment materials, such as
those discussed above, this feature allows positioning of the
discharge opening 95 to direct the pre-treatment materials where
they are needed.
In certain embodiments, the lumen 88 can be provided with a seal
89, which can be in the form of an elastomeric seal ring. The seal
89 can form a fluid-tight seal around the injection tube 94, which
can be especially important where the biomaterial is injected under
pressure. In addition, the seal 89 can operate as a form of joint
to support the injection tube 94 as the discharge opening 95 is
manipulated within the disc cavity.
In another feature of the invention, the cannulated distractor can
provide a vent for the discharge of excess biomaterial when the
disc cavity C is full. The vent is particularly useful where the
biomaterial is introduced under gravity feed. In one specific
embodiment, a vent hole 92 is provided in the distractor 85. When
the disc cavity is full, the biomaterial will seep through the vent
opening 92, providing a direct visual indication that the cavity is
full. Preferably, the vent opening 92 includes a tube that projects
away from the cannulated distractor 85 to improve the visibility of
the vent in situ. Alternatively, the vent can be formed by a
difference in diameter between the injection tube 94 and the lumen
88, and in the absence of the seal 89.
The vent 92 is well-suited to procedures involving gravity feed of
the biomaterial into the disc space. However, the vent can also be
useful where the material is fed under pressure. For example, the
vent 92 can be maintained initially open as the biomaterial is
injected into the cavity C through the injection tube 94. When the
cavity is completely full, biomaterial will seep from the vent 92.
As this point, the vent can be closed and additional biomaterial
injected into the disc space to increase the pressure within the
cavity C. The seeping through the vent provides an immediate
indication that the cavity is full, and can provide a starting
point for the introduction of a calibrated amount of additional
biomaterial to achieve a proper cavity pressure.
With each of the embodiments, once the biomaterial has cured and
the cannulated distractor removed, the portal or portals in the
disc annulus can be filled to prevent herniation of the newly
formed prosthetic disc material. The annular portal can be sealed
with any suitable material, such as fibrin glue, or a polymerizable
material, or the like. The material used to seal the annulus should
be sufficiently strong to remain intact as the intradiscal pressure
is increased due to hydration or biomechanical movement of the
spine.
In accordance with certain embodiments, the cannulated distractors,
and particularly the distraction tips, described above can be
formed a variety of bio-compatible materials. As explained above
the distraction tips must be sufficient strong to maintain proper
distraction of the disc space until the biomaterial has been fully
injected and cured, if necessary. In certain embodiments, the
distraction tips are formed of a bio-compatible metal, such as
stainless steel or titanium. In other embodiments, the distraction
tips are formed of a polymer or plastic that is preferably
radiolucent to permit visualization of the distraction tip in situ
to verify the position of the component.
While the invention has been illustrated and described in detail in
the drawings and foregoing description, the same should be
considered as illustrative and not restrictive in character. It is
understood that only the preferred embodiments have been presented
and that all changes, modifications and further applications that
come within the spirit of the invention are desired to be
protected.
* * * * *
References